TERM

NAME
DESCRIPTION
PORTABILITY
FILES
SEE ALSO

NAME

term - conventions for naming terminal types

DESCRIPTION

The environment variable TERM should normally contain
the type name of the terminal, console or display-device
type you are using. This information is critical for all
screen-oriented programs, including your editor and
mailer.

A default TERM value will be set on a per-line basis
by either /etc/inittab (Linux and System-V-like
UNIXes) or /etc/ttys (BSD UNIXes). This will nearly
always suffice for workstation and microcomputer
consoles.

If you use a dialup line, the type of device attached to it
may vary. Older UNIX systems pre-set a very dumb terminal
type like `dumb' or `dialup' on dialup lines. Newer ones may
pre-set `vt100', reflecting the prevalence of DEC
VT100-compatible terminals and personal-computer
emulators.

Modern telnets pass your TERM environment variable
from the local side to the remote one. There can be problems
if the remote terminfo or termcap entry for your type is not
compatible with yours, but this situation is rare and can
almost always be avoided by explicitly exporting `vt100'
(assuming you are in fact using a VT100-superset console,
terminal, or terminal emulator.)

In any case, you are free to override the system TERM
setting to your taste in your shell profile. The
tset(1) utility may be of assistance; you can give it
a set of rules for deducing or requesting a terminal type
based on the tty device and baud rate.

Setting your own TERM value may also be useful if you
have created a custom entry incorporating options (such as
visual bell or reverse-video) which you wish to override the
system default type for your line.

Terminal type descriptions are stored as files of capability
data underneath /usr/share/terminfo. To browse a list of all
terminal names recognized by the system, do

toe | more

from your shell. These capability files are in a binary
format optimized for retrieval speed (unlike the old
text-based termcap format they replace); to examine
an entry, you must use the infocmp(1) command. Invoke
it as follows:

infocmp entry-name

where entry-name is the name of the type you wish to
examine (and the name of its capability file the
subdirectory of /usr/share/terminfo named for its first
letter). This command dumps a capability file in the text
format described by terminfo(5).

The first line of a terminfo(5) description gives the
names by which terminfo knows a terminal, separated by `|'
(pipe-bar) characters with the last name field terminated by
a comma. The first name field is the type's primary
name, and is the one to use when setting TERM.
The last name field (if distinct from the first) is actually
a description of the terminal type (it may contain blanks;
the others must be single words). Name fields between the
first and last (if present) are aliases for the terminal,
usually historical names retained for
compatibility.

There are some conventions for how to choose terminal
primary names that help keep them informative and unique.
Here is a step-by-step guide to naming terminals that also
explains how to parse them:

First, choose a root name. The root will consist of a
lower-case letter followed by up to seven lower-case letters
or digits. You need to avoid using punctuation characters in
root names, because they are used and interpreted as
filenames and shell meta-characters (such as !, $, *, ?
etc.) embedded in them may cause odd and unhelpful behavior.
The slash (/), or any other character that may be
interpreted by anyone's file system (, $, [,?), is
especially dangerous (terminfo is platform-independent, and
choosing names with special characters could someday make
life difficult for users of a future port). The dot (.)
character is relatively safe as long as there is at most one
per root name; some historical terminfo names use
it.

The root name for a terminal or workstation console type
should almost always begin with a vendor prefix (such as
hp for Hewlett-Packard, wy for Wyse, or
att for AT
vt for the VT series of terminals from
DEC, or sun for Sun Microsystems workstation
consoles, or regent for the ADDS Regent series. You
can list the terminfo tree to see what prefixes are already
in common use. The root name prefix should be followed when
appropriate by a model number; thus vt100,
hp2621, wy50.

The root name for a PC-Unix console type should be the OS
name, i.e. linux, bsdos, freebsd,
netbsd. It should not be console or any
other generic that might cause confusion in a multi-platform
environment! If a model number follows, it should indicate
either the OS release level or the console driver release
level.

The root name for a terminal emulator (assuming it doesn't
fit one of the standard ANSI or vt100 types) should be the
program name or a readily recognizable abbreviation of it
(i.e. versaterm, ctrm).

Following the root name, you may add any reasonable number
of hyphen-separated feature suffixes.

2p

Has two pages of memory. Likewise 4p, 8p, etc.

mc

Magic-cookie. Some terminals (notably older Wyses) can only
support one attribute without magic-cookie lossage. Their
base entry is usually paired with another that has this
suffix and uses magic cookies to support multiple
attributes.

am

Enable auto-margin (right-margin wraparound)

m

Mono mode - suppress color support

na

No arrow keys - termcap ignores arrow keys which are
actually there on the terminal, so the user can use the
arrow keys locally.

nam

No auto-margin - suppress am capability

nl

No labels - suppress soft labels

nsl

No status line - suppress status line

pp

Has a printer port which is used.

rv

Terminal in reverse video mode (black on white)

s

Enable status line.

vb

Use visible bell (flash) rather than beep.

w

Wide; terminal is in 132 column mode.

Conventionally, if your terminal type is a variant intended
to specify a line height, that suffix should go first. So,
for a hypothetical !FuBarCo? model 2317 terminal in 30-line
mode with reverse video, best form would be
fubar-30-rv (rather than, say,
`fubar-rv-30').

Terminal types that are written not as standalone entries,
but rather as components to be plugged into other entries
via use capabilities, are distinguished by using
embedded plus signs rather than dashes.

Commands which use a terminal type to control display often
accept a -T option that accepts a terminal name argument.
Such programs should fall back on the TERM
environment variable when no -T option is
specified.

PORTABILITY

For maximum compatibility with older System V UNIXes, names
and aliases should be unique within the first 14
characters.

Please note that any user can change the contents of pages on this site,
and therefore the Waikato Linux Users Group can offer no assurances that
the information is correct, and the information on this site is not
necessarily the opinion of the Waikato Linux Users Group, or any of its
members. If you have any complaints about the contents of this page,
please do not hesitate to contact the Waikato Linux Users Group, or, click
the Edit button!

Unless otherwise noted, all pages on this site are licensed under the
WlugWikiLicense.